For security reasons it is possible to use a VOS identifier (an unique identification character
string, also called masked call sign). Contrary to the official call sign there will be no public
access to the ID's, so it won't be possible to link a VOS ID (masked call sign) with a specific
ship. This option should be used ONLY in consultation with the National Meteorological
Service or PMO. If a VOS ID is inserted then this ID will be used in the real time observation
and the call sign only in the stored (climatological) log. Format: any combination of upper case
letters (A-Z) and numbers (0 - 9)